1. Field of the Invention
The present invention concerns methods and devices for position determination of body matrix coils in MR systems.
2. Description of the Prior Art
Magnetic resonance apparatuses for examination of patients in particular via magnetic resonance tomography (MR) are known from DE10314215B4, for example.
Modern magnetic resonance system operate with coils to emit radio-frequency pulses for excitation of nuclear spins and/or to receive the induced magnetic resonance signals. A magnetic resonance system typically has a permanent magnet or (more often) a superconducting coil that generates a basic magnetic field (H0) that is optimally homogeneous, a whole body coil (also called a body coil or BC) that is large and is normally installed permanently in the MR apparatus, and multiple small local coils (also called surface coils or LCs). To obtain data from which images of a patient can be generated, selected regions of the subject or patient to be examined are read out with gradient coils for three axes (for example X, Y approximately radial to the patient, Z in the longitudinal direction of the patient). The spatial coding in magnetic resonance tomography is typically produced by a gradient coil system with three independently controllable, magnetically orthogonal gradient field coil systems. By overlaying the three, freely scalable fields (in three directions X, Y, Z), the orientation of the coding plane (‘gradient field’) can be freely selected.
In an MR examination, local MR coils (local coils) composed of a housing and one or more antenna coils (resonators) that can be substantially freely positioned on the surface of the patient to be examined (thus “anterior” if the patient is located in a dorsal position) are frequently used to transmit and/or receive. For an MR examination there are advantages to knowing the position of the MR coils in the z-direction (the z-direction corresponds to the longitudinal axis of the patient bed on which the patient lies). Workflows can be accelerated and be designed more comfortably with this knowledge since a scanner or computer controlling the examination workflow can take on large parts of the positioning and selection of the correct coils in the case of particular body regions to be scanned. Conventionally, an overview MR image has been produced at the beginning of an imaging examination of a patient, from which overview MR image the positions of the local coils can be automatically calculated if the characteristic antenna profiles of the MR antennas are known.